This invention relates to means for inspecting ring-like work elements to rapidly and efficiently determine the concentricity and wall thickness of the workpiece.
Until recently, most cylindrical or ring-like work pieces were inspected by hand using a micrometer or a "go-no go" gauge. This type of procedure was tedious, time consuming and highly susceptible to human error. An automatic device, which was capable of rapidly and accurately inspecting annular workpieces, was developed by Lauri and is disclosed in his U.S. Pat. No. 3,028,676. In the Lauri device, the workpiece was placed within a horizontally mounted drum with the outside wall of the work resting against the inner wall of the drum. A stylus was then rotated rapidly inside the work about the axis of the drum at a prescribed radius whereby the stylus would touch the inner wall of the work when it was out of tolerance and, in response thereto, generate an alarm signal. In practice, the work element was rolled by hand about the inside of the drum which enabled the more rapidly moving stylus to interrogate an infinitely large number of points about the work in a very short period of time.
The above noted Lauri device proved to be a most expedient and economical instrument and, as a result, was readily accepted by industry. However, the relatively delicate stylus utilized therein was difficult to set up and adjust for different size workpieces and could be adversely affected by dirt and other types of contamination. Similarly, because the operator of the machine was required to perform some hand operations during the test period, the results obtained were sometimes subject to human error.